Silicone resins having phenyl groups and methylphenylpolysiloxanes that are exemplary of phenylsilsesquioxane resins are widely used as components of cosmetic compositions and use thereof in order to impart glossiness to hair and the like is known (e.g. see Patent Document 1). Additionally, methylphenylpolysiloxane, known by the INCI name “Phenyl trimethicone” is used widely in the field of cosmetic compositions as it can impart shine and luster to a cosmetic composition (see Patent Document 2). Furthermore, silicone compounds having phenyl groups are widely known as having high refractive indices and it is also known that, in the control of the refractive index, the refractive index can be raised by introducing a phenyl group as a substituent on a polysiloxane sidechain (e.g. see Non-Patent Documents 1 and 2). Additionally, Patent Document 3 describes a cosmetic composition having a superior feeling of sheerness and luster comprising an alkylphenylpolysiloxane, wherein a phenyl group content is not less than 50%, as an essential component.
However, while the feeling of sheerness and the refractive index of a silicone resin having a phenyl group is superior, viscosity adjustment thereof is difficult and it is not possible to maintain the overall refractive index of the composition when diluted using an ordinary silicone oil to 1.50 or greater (more preferably from 1.55 to 1.60). Thus, there is a problem in that the refractive index declines, which leads to insufficient luster of the cosmetic composition. On the other hand, while the refractive index of methylphenylpolysiloxane is superior, it is generally difficult to set the phenyl group substitution ratio to 50% or greater and easily produce a highly viscous methylphenylpolysiloxane such as one with a viscosity greater than 200 mPa·s. Furthermore, chain methylphenylpolysiloxanes do not have a three-dimensionally crosslinked structure and, therefore, have low viscosity, are prone to elute from cosmetic compositions. Moreover, when a chain methylphenylpolysiloxane is compounded alone, sufficient satisfaction cannot be obtained with regards to the imparting of lasting luster to the cosmetic composition and improvement in sensation during use.
Patent Document 4 describes an alkyl-phenyl silsesquioxane resin composition useful in personal care compositions and the like, which enhances the durability and retention of a powder agent after application. Patent Document 5 describes a cosmetic composition for the purpose of imparting luster and the like, the composition comprising a propylphenylsilsesquioxane resin having a weight average molecular weight of 2,000 to 30,000, a phenyl silicone or similar aromatic solvent, and optional cosolvent.
Compositions comprising these propylphenylsilsesquioxane resins have a high refractive index. However, while a certain degree of effects are displayed in imparting lasting luster to a cosmetic composition, there is a demand for further improvement in the appearance and sensation during use thereof. Furthermore, in such a composition, compatibility particularly with the propylphenylsilsesquioxane resin and the phenyl silicone is insufficient and, as a result, separation of the oil components is prone to occur. Thus, there is a problem in that a uniform composition cannot be easily obtained. Particularly, there is a problem in that the storage stability of a cosmetic composition comprising said component is insufficient. Moreover, there is another problem in that it is difficult to control the viscosity. Furthermore, in a system containing both silicone powder and phenyl silicone oil, while sensation during use is improved, there is a demand for further improvement with regards to appearance such as shine and brilliance and attaining a sufficient refractive index and feeling of sheerness. Additionally, satisfactory storage stability cannot be obtained.
In an effort to resolve these problems, the present applicant proposed the phenyl group-containing organopolysiloxane composition recited in Patent Document 6. The phenyl group-containing organopolysiloxane composition comprises: (A) a phenylsilsesquioxane resin having a weight average molecular weight within a range of 500 to 2,000 and at least 15 mol % of the siloxy units constituting the resin are the phenyl siloxy unit: (C6H5SiO3/2); and (B) a phenyl group-containing organopolysiloxane that is liquid at 25° C. and that has a refractive index of 1.45 or greater, in predetermined ranges. With this phenyl group-containing organopolysiloxane composition, an overall refractive index of the composition is high, and the phenylsilsesquioxane resin and the phenyl group-containing organopolysiloxane are uniformly miscible with each other and, therefore, compounding stability in a cosmetic composition and handling are superior and the viscosity can be easily adjusted.
However, in these prior art documents, there is no recitation of a branched silicone-based oil agent such as the liquid aryl group-containing polyorganosiloxane of the present invention. Furthermore, structurally, with the TPh type phenylsilsesquioxanes used in the Practical Examples and the like in Patent Documents 1 to 6, the content of the phenyl groups per one mole of Si atoms is not greater than 1.0. Moreover, there is no mention whatsoever of an aryl group-containing polyorganosiloxane in which it is preferable to set the content of T branch units to be 50 mol % or less. Furthermore, there is no specific recitation of a liquid aryl group-containing polyorganosiloxane in which the content of T-type arylsiloxy units is limited and the content of phenyl groups per one mole of Si atoms is greater than 1.0. Thus, there is no recitation or implication whatsoever regarding the existence of technical problems and the technical benefits of such an aryl group-containing polyorganosiloxane having superior stability in a composition when mixed with an oil agent, and being able to be stably compounded in a non-aqueous cosmetic composition without turbidity that accompanies hydrolysis occurring.